The bioaccumulations of metals Cu, Cd, Ni, Cr, Co, Mn, Zn and Fe were measured in bivalves,Cerastoderma glucaum, and four species of fishes includingAlburnus chalcoides,Liza aurata, Rutilus frisii andSander lucioperca from various trophic levels of the Caspian food web. The concentrations of Cd, Cr, Co and Ni in most samples of fish were below the detection limits; while the concentrations were detected in most samples of bivalveC. glucaum. The stable nitrogen isotope ratios varied among the samples fromC. glucaum (δ15N=3.5 ‰) to S. lucioperca (δ15N=13.1‰). Among the four fish species, while the highest concentrations of Mn, Ni and Fe were observed inL. aurata,the lowest concentrations of Mn and Fe were observed inS. lucioperca. These species also had the lowest and highest trophic levels with an average of 3.3 and 4.2, respectively. No accumulation of metals with increase in body size was observed in muscles of species from different trophic levels. The comparison of metal concentrations with the health guidelines for human consumption showed that those intakes were lower than the legislated limits. While there was a strong relationship between trophic levels and body size ofA. chalcoides andR.frisii, no significant slopes were observed between the total lengths (TLs) and the Ln concentrations of metals. It is necessary to determine metal concentrations in food resources of fish species, particularly inR.frisii that has significantly different δ15N in relation to body size.

Keywords:Metal pollution, Bioaccumulation, Stable isotope, Caspian Sea